The Air Force's struggling tanker program is facing questions about its ability to withstand electromagnetic pulses

U.S. Air Force photo/Jet FabaraA KC-46 Pegasus takes its first flight at Paine Field in Everett, Washington, September 25, 2015.

The Pentagon’s office of operational test and evaluation says the Air Force’s new KC-46A Pegasus tanker may not be fully resistant to an electromagnetic pulse.

The Air Force and Boeing should conduct more tests to determine the survivability of the tanker’s systems, the office says.

The Air Force and Boeing have said the aircraft passed EMP testing as mandated by the established KC-46 testing plan.

The Air Force’s and Boeing’s development of the new KC-46A Pegasus tanker has been waylaid by cost overruns and operational issues over the past several years.

Officials from the Air Force and Boeing have said that significant lingering problems, like contact between the KC-46’s refuelling boom and the receiving aircraft during refuelling, are expected to be resolved this year, ahead of Boeing’s October deadline to deliver 18 of the new tankers.

However, a report from the Pentagon’s Director of Operational Test and Evaluation has cautioned that while the KC-46’s most important systems could operate under EMP conditions, its operational capabilities in such a scenario have not been fully tested.

“While testing indicated the KC-46A flight-critical systems and boom refuelling systems are likely survivable to the 6 decibel (dB) contractual requirement, the Program Office approved verification plan did not demonstrate the residual KC-46A mission systems capability during such an event,” according to the report, which covers fiscal year 2017 and was released last week.

“The program uninstalled or deactivated multiple mission critical systems prior to testing and, therefore, their EMP tolerance was not tested on an aircraft in a mission-representative configuration,” the DOT&E report said. “The program pre-deployed the refuelling boom with hydraulics deactivated for the EMP test and therefore the capability to deliver fuel during or immediately following the EMP event was not tested.”

The KC-46 underwent EMP testing in July at Naval Air Station Patuxent River in Maryland and at Edwards Air Force Base in California. During the testing in Maryland, the plane received pulses from “a large coil/transformer” above the aircraft, designed to evaluate its “ability to safely operate through electromagnetic fields … under mission conditions,” Boeing said at the time.

The DOE&T report said no tests were conducted with all flight and mission systems activated – a step required to fully test the aircraft under EMP conditions. But representatives from the Air Force and Boeing said the KC-46 had proven its EMP functionality as mandated by its test plan.

Air Force spokesman Maj. Emily Grabowski told Inside Defence that mission-critical systems has passed testing and that the systems the DOT&E report highlighted are “non-critical.” Grabowski added that, overall, the KC-46 met system specifications and that the Air Force was working with DOT&E to “reconcile” concerns raised in the report.

Charles Ramsey, a spokesman for Boeing, said EMP testing was conducted according to the Air Force’s test plan and that systems designated critical by that plan showed their functionality on a subsequent flight. “There are no EMP issues on the KC-46,” he told Inside Defence.

The Air Force is planning two tests related to nuclear threats during fiscal year 2018, which began in October and ends in September. One will evaluate the KC-46s ability to launch and fly a safe distance from a simulated nuclear attack on its base, and the other will test the tanker’s “inherent nuclear hardness” to blast, radiation, flash, thermal, and EMP effects, according to the DOT&E report.

The DOT&E report also notes that the KC-46 contract was awarded with a six-decibel threshold for the aircraft – a standard that the aircraft met during testing in July. However, after the contract was signed, the US military imposed a new 20-decibel standard tanker aircraft.

Without further testing, the report says, the Air Force and US Strategic Command will not know if the tanker meets that new requirement. “The Air Force should re-test the KC-46A in an operationally representative condition to determine the actual EMP design margin,” the report concludes.

‘They’re going to clear out pretty quick’

In December, the FAA granted Boeing an amended type certificate for the Boeing 767-2C, which is the baseline aircraft for the KC-46. The firm still needs to get an FAA supplemental type certificates for the military and aerial-refuelling systems needed so the 767-2C can function as a KC-46. Additional tests are expected during the final review process.

The Air Force currently expects to receive the first operational KC-46s by late spring. Air Force Gen. Carlton Everhart, chief of Air Mobility Command, told Air Force Times in December that once testing is finished and the new tankers star arriving, he expects “they’re going to clear out pretty quick” to Air Force bases.

Boeing won the KC-46 program contract 2011, and the Air Force plans to buy 179 KC-46s under the $US44.5 billion program. As a part of the contract, Boeing is responsible for costs beyond the Air Force’s $US4.82 billion commitment, and as of late 2017, the defence contractor had taken on about $US2.9 billion in pretax costs.

Defence Secretary Jim Mattis has had limited involvement in Pentagon weapons programs, but he issued a stark warning to acquisition officials in November, saying he was “unwilling (totally)” to accept flawed KC-46 tankers.